1. Field of the Invention
The present invention relates to a method of manufacturing a complex body of a sintered ceramic material and a metal.
2. Description of the Prior Art
Although ceramic materials have relatively a high compressive strength, they have a low tensile strength and impact resistance. To compensate for these weaknesses, the combination of a ceramic material with a metal has recently been studied. Shrink fitting and cast-embedding are well known methods of forming such a combination.
Although shrink fitting is a simple means of forming this combination, it has disadvantages because the shapes of ceramic material capable of being shrink fitted are quite limited and stress will act on the shrink fitted combination only in a fixed direction. For these reasons, the types and uses of products formed by shrink fitting are limited.
In contrast with the above, the cast-embedding method has advantages because ceramic material is strong against compressive stress and the cast-embedding method can be used to form a product of complicated shape. However, the cast-embedding method has a problem because it results in a cavity being formed between the ceramic material and the metal, thus rendering the casting of the metal on the ceramic material imperfect. This cavity formation is caused by a number of factors such as the low wettability of the ceramic material by the molten metal, gas in the molten metal, and moisture in the ceramic material if it is porous. A stress differential arises between a product portion which has a cavity between the ceramic material and the metal and another product portion where the ceramic material and the metal are in contact with each other. As a result, the ceramic material undergoes a shear fracture. To prevent the formation of the cavity, conventional measures such as preheating the ceramic material and coating the surface of the ceramic material have been taken. However, these measures are not completely effective and increase the cost of production.